Process of rendering glue waterproof



Patented Feb. 12, 1929.

STATES PATE T OFFICE.

PROCESS OF BENDERING GLUE WATERPROOF.

Ito Drawing. Application filed April 2,

My invention has for its object to improve the waterproof qualities of glue, and more especially of casein glues used to glue up or unite the various veneers of what is known as plywood. The better grades of casein glue hitherto on the market have a fairly high waterproofing quality, but none thereof have met the severe tests required to ass the grade A specification of the United tates Government Bureau of Standards. This grade A demands a very high waterproofing quality, such high quality being required for various kinds of work, such as aeroplanes, pontoons,

boats, and the woodwork of staterooms of 5 liners or sea-going vessels.

l have discovered a simple process by which I can give to casein glues the additional water-resisting qualit required, for example, to meet the grade A a ove referred to. More definitely stated, I have discovered that formaldehyde will act upon casein glues to produce the said increased water-proofing quality. In carryin out this process, the casein glue, before eing subjected to the action of formaldehyde, is used to glue up the various veneers or elements of the plywood and the glue, after it has set, is subjected to the action of formaldehyde. .When the freshly glued plywood has been allowed so to stand under pressure for a few hours, more or less, depending on the characteristics of the glue used, it is removed from the clamps or press and is then treated with formalde hyde or formaldehyde compound. Under this treatment, the pores of t e wood absorb the formaldehyde to such an extent that it penetrates through the veneers to the glue line or joint and, upon contact of the formaldehyde with the casein, there is formed a compound whose nature issuch that it is extremely insoluble in water. As an illustration of the extreme insolubility or waterresisting qualities of the lue thus treated, it may be stated that l ave soaked ply wood, made and treated as above described, in water for a year Without appreciably loosening the veneers.

After the plywood has been treated by this improved process, the panels or glued-up parts are advisably allowed to season for a few days in a well-ventilated lace where the odor of the formaldehyde will be caused to disappear. 'lho'treatment does not stain or in any way harm the veneer of which the 1927. Serial No. 180,624.

plywood is composed. The formaldehyde may be applied either in the form of a soluhonor in gaseous form, and it may be of varying strength. On the market, the formaldehyde is usually purchased in a forty percent (40%) solution, but, of course, I will not 1n any way limit myself to the strength of such solution. The solution may be sprayed on the wood or the wood may be dipped in the solution or the solution may be ap lied by the use of a sponge. Within reasonable lengths, the-stronger the solution, the quicker is the Water-proofing action.

Another good method of treatment is to take the plywood from the pressure device and loosely stack it in a closed room or chamber and there subject it to formaldehyde gas. The gas may be generated in the room or enclosure by oxidizing methyl alcohol in a special burner, such as is frequently used for fumigating.

From what has been said, it will be understood that I do not limit myself to the particular way of bringing the formaldehyde into contact with the casein glue, but desire to claim the same broadly. 'I have also found that formaldehyde Will, to some extent, increase the waterproofing quality even in animal glues.

In practice l have obtained the results above outlined by the use of formaldehyde either in the form of gas or liquid solution but it is possible that other coagulants may be found useful for the same purpose. lhe important feature of this case is in the time and manner in which the formaldehyde or glue coagulant is applied. The formaldehyde influid form, that is, in either liquid solution or in gaseous form, is applied through the pores of the outer wooden plies or portions and comes into contact with the glue which has already hardened and permanently united the wood elements. lin this process the waterproofing action of the formaldehyde may be applied long after the glue has hardened and long after the wooden article has been manufactured. As is evident, this rocess could be carried out only in uniting e ements such as wood that are porous so that the liquid or gaseous formaldehyde can reach the glue which, in the completed ply wood or article, is then covered by the outer wooden plies or sections.

While this improved process is especially kinds of multi-section wooden or similar porous articles where glue has been previously set to connect wood sections.

What I claim is:

1. The process of increasing the waterproof quality of set glue in previously manufactured multi-section porous articles which consists in applying a fluid glue coagulant to the set glue through the pores of the material.

2. The rocess of increasing the waterproof quality of set glue in previously manufactured multi-section wooden articles which consists in applying fluid formaldehyde to set glue through the pores of the wood.

3. The process of increasing the waterproof quality of set glue in multi-section wooden articles which consists first in applying glue between the wood elements and allowing the glue to set and permanently unite with the contacting wood, and in thereafter subjecting the glue and the united portions of the wood to the action of a fiuid glue coagulant applied thereto through the pores of the wood.

4. The process of increasing the waterproof quality of set glue in multi-section wooden articles which consists first in applying glue between the wood elements and allowing the glue to set and permanently unite with the contacting wood,-and in thereafter subjecting the glue and the united portions of the wood to the action of formaldehyde applied thereto through the pores of the wood.

5. The process of increasing the waterproof quality of set glue in multi-section wooden articles which consists first in applying casein glue to connect the wood elements and allowing the glue to set and permanently unite with the contacting wood, and in thereafter subjecting the set casein glue and the connected portions of the wood to the action of formaldehyde applied thereto through the pores of the wood.

In testimony whereof I affix my signature.

HENRY L. PRESTHOLDT. 

